Known as particulate porous carbon materials are activated carbon having both relatively large macropores and micropores, including granular activated carbon and activated-carbon fibers, and fine carbons represented by carbon nanotubes, meso-porous carbon produced from meso-porous silica or zeolite templates, etc.
These particulate porous carbon materials have not only the high chemical stability, electrical conductivity, and thermal conductivity which are possessed by the carbon but also large surface areas due to the pores. Owing to such properties, these carbon materials have been utilized as battery materials, adsorbent materials, catalyst supports, etc.
In particular, carbon materials produced from carbon nanotubes are attracting attention because of the high electrical conductivity and thermal conductivity thereof, and attempts are being made to create a functional material so as to take advantage of these properties. For example, Patent Document 1 describes a vapor-phase-process carbon fiber (carbon nanotube) having a branch portion. Patent Document 2 describes a bundle of carbon nanotubes, in which the ends on one side have been connected to each other by a carbon network.